U.S. patent application number 14/910323 was filed with the patent office on 2016-07-21 for curable epoxy compositions.
The applicant listed for this patent is DOW GLOBAL TECHNOLOGIES LLC. Invention is credited to William W. FAN, Yi Ling LIANG, Stanley E. MOORE, Mark B. WILSON, Rui XIE.
Application Number | 20160208091 14/910323 |
Document ID | / |
Family ID | 51619330 |
Filed Date | 2016-07-21 |
United States Patent
Application |
20160208091 |
Kind Code |
A1 |
LIANG; Yi Ling ; et
al. |
July 21, 2016 |
CURABLE EPOXY COMPOSITIONS
Abstract
Curable compositions comprising an epoxy mixture comprising a)
an epoxy mixture comprising i) a first epoxy component comprising
epoxy phenol novolac oligomers having a content of 2-functional
monomers of less than 10 weight percent based on the total weight
of the first epoxy component and having an epoxide equivalent
weight in the range of 170 to 200; and ii) a second epoxy component
comprising an epoxy resin having monomers with an average
functionality of at least 2 and b) a hardener, are disclosed. The
curable compositions can be used to prepare prepregs for hot-melt
applications.
Inventors: |
LIANG; Yi Ling; (Pearland,
TX) ; FAN; William W.; (Lake Jackson, TX) ;
MOORE; Stanley E.; (Lake Jackson, TX) ; XIE; Rui;
(Pearland, TX) ; WILSON; Mark B.; (Clute,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DOW GLOBAL TECHNOLOGIES LLC |
Midland |
MI |
US |
|
|
Family ID: |
51619330 |
Appl. No.: |
14/910323 |
Filed: |
September 16, 2014 |
PCT Filed: |
September 16, 2014 |
PCT NO: |
PCT/US2014/055888 |
371 Date: |
February 5, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61882940 |
Sep 26, 2013 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08J 2363/04 20130101;
C08G 59/08 20130101; C08L 63/00 20130101; C08J 2363/00 20130101;
C08G 59/44 20130101; C08L 63/04 20130101; C08G 59/686 20130101;
C08J 5/24 20130101 |
International
Class: |
C08L 63/00 20060101
C08L063/00; C08J 5/24 20060101 C08J005/24; C08G 59/68 20060101
C08G059/68; C08G 59/08 20060101 C08G059/08; C08G 59/44 20060101
C08G059/44 |
Claims
1. A curable composition comprising: a) an epoxy mixture comprising
i) a first epoxy component comprising epoxy phenol novolac
oligomers having a content of 2-functional monomers of less than 10
weight percent based on the total weight of the first epoxy and
having an epoxide equivalent weight in the range of 170 to 200 ii)
a second epoxy component comprising an epoxy resin having monomers
with an average functionality of at least 2 wherein the first epoxy
is present in the range of from 10 weight percent to 90 weight
percent and the second epoxy is present in the range of from 0
weight percent to 97 weight percent, based on the total weight of
the epoxy mixture; and b) a hardener.
2. A curable composition in accordance with claim 1 wherein the
first epoxy component comprises less than 5 weight percent of
2-functional monomers based on the total weight of the first epoxy
component.
3. A curable composition in accordance with claim 1 wherein the
first epoxy component has an average functionality of from 4.0 to
5.0 epoxy groups per molecule.
4. A curable composition in accordance with claim 1 wherein the
first epoxy component has an average functionality of from 4.2 to
4.8 epoxy groups per molecule.
5. A curable composition in accordance with claim 1 wherein the
first epoxy component comprises less than 5 weight percent of
2-functional monomers, in the range of from 15 weight percent to 20
weight percent of 3-functional monomers, in the range of from 10
weight percent to 20 weight percent of 4-functional monomers, in
the range of from 10 to 20 weight percent of 5-functional monomers,
and in the range of from 50 weight percent to 60 weight percent of
6-functional monomers, based on the total weight of the first epoxy
component.
6. A curable composition in accordance with claim 1 wherein the
hardener is selected from the group consisting of aliphatic amines,
modified aliphatic amines, cycloaliphatic amines, modified
cycloaliphatic amines, amidoamines, dicyanopolyamide, polyamide,
tertiary amines, aromatic amines, anhydrides, mercaptans, cyclic
amidines, isocyanate cyanate esters, phenolic hardeners and
combinations thereof.
7. A curable composition in accordance with claim 1 wherein the
curable composition does not contain a solvent.
8. A curable composition in accordance with claim 1 further
comprising a catalyst.
9. A curable composition in accordance with claim 1 having a
complex shear modulus in the range of from 0.3 MPa to 0.03 MPa at
conditions of under 25.degree. C. and 1 rad/s and a glass
transition temperature (T.sub.g) that is equal to or greater than
the final curing temperature when the prepreg is cured for less
than two hours.
10. A hot melt prepreg prepared from the curable composition of
claim 1.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] Embodiments of the present disclosure relate to epoxy
compositions and in particular to epoxy compositions that are
combined with hardeners to form curable compositions. The curable
compositions can be used to prepare prepregs.
[0003] 2. Description of Background and Related Art
[0004] Epoxy thermosets have been used as the resin matrix to embed
reinforced fibers to prepare lightweight and high strength
composite articles for structural purposes. Among various composite
manufacturing processes, the hot-melt prepreg process is a
preferred process because it provides consistent properties and
ease of use for composite fabricators, particularly in sporting
goods, aerospace, automotive and other applications.
[0005] "Hot-melt" prepregs presented herein refer to fibers
impregnated with solvent free, un-cured or slightly cured epoxy
formulations. A typical manufacturing procedure involves (1) film
manufacture and (2) film impregnation.
[0006] Many different types of high functional epoxy resins have
been used to achieve high glass transition temperatures (T.sub.g)
of the cured epoxy thermosets to shorten de-molding time. However,
the usage of these high functional epoxy resins may also cause a
loss of adequate tackiness, and an increase in the melt viscosity
of the resin blend, which can lead to insufficient resin wetting of
the impregnated fibers, the formation of voids between the layered
structures in composite articles, and a difficulty of preparing
melt-epoxy-resin blends.
[0007] Therefore, a curable composition useful for preparing
hot-melt prepregs which provides (1) adequate tack to serve as a
semi-permanent adhesive (2) high glass transition temperature
(T.sub.g) and (3) an adequate viscosity profile for hotmelt prepreg
processing is desired.
SUMMARY OF THE INVENTION
[0008] In one broad embodiment of the present invention, there is
disclosed a curable composition comprising, consisting of, or
consisting essentially of: a) an epoxy mixture comprising i) a
first epoxy component comprising epoxy phenol novolac oligomers
having a content of 2-functional monomers of less than 10 weight
percent based on the total weight of the first epoxy component and
having an epoxide equivalent weight in the range of 170 to 200 and
ii) a second epoxy component comprising epoxy resin oligomers
having monomers with an average functionality of at least 2 and b)
a hardener.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a plot of temperature versus heat flow.
DETAILED DESCRIPTION OF THE INVENTION
[0010] In various embodiments, the curable composition comprises an
epoxy mixture; and b) a hardener.
Epoxy Mixture
[0011] The composition contains an epoxy mixture. The mixture
comprises i) a first epoxy component comprising epoxy phenol
novolac oligomers having a content of 2-functional monomers of less
than 10 weight percent based on the total weight of the first epoxy
component and having an epoxide equivalent weight in the range of
170 to 200 and ii) a second epoxy component comprising an epoxy
resin having monomers with an average functionality of at least
2.
[0012] The first epoxy component comprises epoxy phenol novolac
oligomers. In an embodiment, the epoxy phenol novolac is phenol
novolac (EPN) and is a bisphenol-F epoxy novolac in yet another
embodiment.
[0013] The general structure of an epoxy phenol novolac is shown in
Formula I, below.
##STR00001##
Formula I
[0014] In an embodiment, the first epoxy component comprises epoxy
novolac oligomers having less than 10 weight percent of
2-functional monomers (2-functional, n=0 in Formula I, above), and
has less than 5 weight percent of 2-functional monomers in another
embodiment.
[0015] Generally, the first epoxy component averages in the range
of from 4.0 to 5.0 epoxide groups per molecule (n=2.0 to 3.0 in
Formula I above), and having an epoxide equivalent weight in the
range of 150 to 220, has in the range of 4.2 to 4.8 epoxide groups
per molecule (n=2.2 to 2.8 in Formula I above) and has an epoxide
equivalent weight in the range of 170 to 200 in another
embodiment.
[0016] The first epoxy component is generally present in the epoxy
mixture in the range from 3 weight percent to 96 weight percent and
is present in an amount in the range of from 10 weight percent to
90 weight percent in other embodiments, based on the total weight
of the epoxy mixture. Concentrations of lower than 3 weight percent
may lead to a low T.sub.g which is insufficient to reduce the
de-molding time, while concentrations of higher than 96 weight
percent may lead to insufficient tack performance for composite
manufacturing.
[0017] In various embodiments, the epoxy mixture further comprises
a second epoxy component comprising an epoxy resin having monomers
with an average functionality of at least 2. In an embodiment, the
second epoxy component can have an average functionality of
2.8.
[0018] The second epoxy component may vary and can include
conventional and commercially available epoxy resins, which may be
used alone or in combinations of two or more. In choosing epoxy
resins for compositions disclosed herein, consideration should not
only be given to properties of the final product, but also to
viscosity and other properties that may influence the processing of
the resin composition.
[0019] Particularly suitable epoxy resins include, but are not
limited to epoxy resins based on reaction products of
polyfunctional alcohols, phenols, cycloaliphatic carboxylic acids,
aromatic amines, or aminophenols with epichlorohydrin. A few
non-limiting embodiments include, for example, bisphenol A
diglycidyl ether, bisphenol F diglycidyl ether, resorcinol
diglycidyl ether, and triglycidyl ethers of para-aminophenols.
Other examples of suitable epoxy resins include but are not limited
to reaction products of epichlorohydrin with o-cresol and,
respectively, phenol novolacs. Further epoxy resins include
epoxides of divinylbenzene or divinylnaphthalene. It is also
possible to use a mixture of two or more epoxy resins.
[0020] The epoxy resins useful in the present invention for the
preparation of the curable compositions may be selected from
commercially available products; for example, D.E.R.RTM.. 331,
D.E.R..RTM. 332, D.E.R.RTM.. 383, D.E.R..RTM. 334, D.E.R.RTM.. 580,
D.E.N.RTM.. 431, D.E.N..RTM. 438, D.E.R.RTM.. 736, or D.E.R.RTM..
732, epoxy resins available from The Dow Chemical Company or Syna
21 cycloaliphatic epoxy resin from Synasia. As an illustration of
the present invention, the additional epoxy resin may be a mixture
of a liquid epoxy resin, such as D.E.R. 383, an epoxy novolac
D.E.N. 438, a cycloaliphatic epoxide Syna 21, and a divinylarene
dioxide, divinylbenzene dioxide (DVBDO) and mixtures thereof.
[0021] The second epoxy component is generally present in the epoxy
mixture in the range of from 0 weight percent to 97 weight percent,
based on the total weight of the epoxy mixture, and is present in
the range of from 10 weight percent to 90 weight percent, based on
the total weight of the epoxy mixture in various other
embodiments.
Hardener
[0022] A hardener can be added to the mixture to form a curable
composition.
[0023] Any suitable epoxy hardener can be used. Examples of epoxy
hardeners that can be used include, but are not limited to
aliphatic amines, modified aliphatic amines, cycloaliphatic amines,
modified cycloaliphatic amines, amidoamines, dicyanopolyamide,
polyamide, tertiary amines, aromatic amines, anhydrides,
mercaptans, cyclic amidines, isocyanates cyanate esters, and the
like. Suitable hardeners include Dicyandiamide (DICY),
bis(4-aminocyclohexyl)methane (AMICURE.RTM. PACM),
diethylenetriamine (DETA), triethylenetetramine (TETA),
aminoethylpiperazine (AEP), isophorone diamine (IPDA),
1,2-diaminocyclohexane (DACH), 4,4'-diaminodiphenylmethane (MDA),
diaminodiphenylsulfone (DDS), m-phenylenediamine (MPD),
diethyltoluenediamine (DETDA), meta-xylene diamine (MXDA),
bis(aminomethyl cyclohexane), dicyandiamide, phthalic anhydride
(PA), tetrahydrophthalic anhydride (THPA), methyltetrahydrophthalic
anhydride (MTHPA), methyl hexahydrophthalic anhydride (MHHPA),
hexahydrophthalic anhydride (HHPA), nadic methyl anhydride (NMA),
benzophenonetetracarboxylic dianhydride (BTDA), tetrachlorophthalic
anhydride (TCPA), and the like, and mixtures thereof.
[0024] Phenolic hardeners can also be used in the thermosetting
composition. Suitable phenolic hardeners include the Rezicure.RTM.
3XXX product line, Meiwa's MEH-XXXX product line or other phenolic
hardeners known to those skilled in the art.
[0025] Generally, the hardener is present in the curable
composition in the range of from 1 to 35 parts per hundred parts
epoxy resin (phr), and from 3 to 30 phr in another embodiment. A
hardener content of less than 1 phr may lead to
insufficiently-cured thermosets that are not capable of providing
desired composite performance
Optional Components
Solvents
[0026] In various embodiments, the curable composition can
optionally further comprise one or more solvents. Examples of
solvents that can be used include, but are not limited to methyl
ethyl ketone (MEK), dimethylformamide (DMF), ethyl alcohol (EtOH),
propylene glycol methyl ether (PM), propylene glycol methyl ether
acetate (DOWANOL.TM. PMA) and mixtures thereof.
[0027] In various other embodiments, no solvent is used.
[0028] Catalysts
[0029] Optionally, catalysts can be added to the curable
composition to facilitate the curing of the formulation. The type
of catalyst depends on the desired end use.
[0030] Examples of catalysts that can be used include, but are not
limited to phenyl dimethyl urea (Omicure U405, CVC Thermoset
Specialty), 4,4' methylene bis phenyl dimethyl urea (Omicure U415,
CVC Thermoset Specialty), cycloaliphatic dimethyl urea (Omicure
U35, CVC Thermoset Specialty), 3, 4 dichlorophenyl dimethyl urea
(Diuron, CVC Thermoset Specialty), and 4 chlorophenyl diemthyl urea
(Monuron, CVC Thermoset Specialty). Other catalyst examples
include, but are not limited to at least one tertiary amine,
including phenolic substituted ones; at least one boric acid-amine
complex; at least one boron trifluoride-amine complex; at least one
imidazole or substituted imidazole; at least one metal
acetylacetonate); at least one transition metal (for example
cobalt, nickel, zinc, chromium, iron, copper) salt; at least one
quaternary ammonium or phosphonium salts; at least one phosphine or
substituted phosphine compound; or a combination thereof.
[0031] Generally, the catalyst is present in the curable
composition in the range of from 0.5 to 10 parts per hundred parts
epoxy resin (phr), and in the range of from 1 to 8 phr in another
embodiment.
[0032] Toughening Agents
[0033] The curable composition can also contain a toughening agent.
In an embodiment, the toughening agent is a core shell rubber.
[0034] A core shell rubber is a polymer comprising a rubber
particle core formed by a polymer comprising an elastomeric or
rubbery polymer as a main ingredient, optionally having an
intermediate layer formed with a monomer having two or more double
bonds and coated on the core layer, and a shell layer formed by a
polymer graft polymerized on the core. The shell layer partially or
entirely covers the surface of the rubber particle core by graft
polymerizing a monomer to the core.
[0035] Generally the rubber particle core is constituted from
acrylic or methacrylic acid ester monomers or diene (conjugated
diene) monomers or vinyl monomers or siloxane type monomers and
combinations thereof.
[0036] The shell layer provides compatibility to the formulation
and has limited swellability to facilitate mixing and dispersion of
the core shell rubber particles in the resin or hardener of the
current invention. In one embodiment the shell does not have
reactive groups towards the epoxy resin or the hardener of the
present invention. Yet in another embodiment the shell might have
reactive groups towards the epoxy resin or the hardener, for
example epoxide or carboxylic acid groups.
[0037] The core shell rubber may be selected from commercially
available products; for example, Paraloid EXL 2650A, EXL 2655,
EXL2691 A, each available from The Dow Chemical Company, or Kane
Ace.RTM. MX series from Kaneka Corporation, such as MX 120, MX 125,
MX 130, MX 136, MX 551, or METABLEN SX-006 available from
Mitsubishi Rayon.
[0038] Polymeric Additives
[0039] Polymeric additives can also be present in the curable
composition. Examples of suitable polymeric additives include, but
are not limited to polyvinylformals (such as Vinylec K and Vinylec
L from Chisso Corp.), polymethylmethacrylates (such as Dianal BR-73
and BR-80 from Dianal America Inc.), polyethersulfones (such as
Sumika Excel 3600P and 5003P from Sumitomo Chemical Co. Ltd.),
polysulfones (such as Ultrason 52010 from BASF), polyimides (such
as Extem Resin VH1003 from Sabic Innovative Plastics), and
polyetherimides (such as Ultem 1010 and ULTEM 1040 from Sabic
Innovative Plastics).
[0040] The curable or thermosettable composition of the present
invention may optionally contain one or more other additives which
are useful for their intended uses. For example, the optional
additives useful in the present invention composition may include,
but not limited to, reactive or non-reactive diluents, stabilizers,
surfactants, flow modifiers, pigments or dyes, matting agents,
degassing agents, flame retardants (e.g., inorganic flame
retardants, halogenated flame retardants, and non-halogenated flame
retardants such as phosphorus-containing materials), curing
initiators, curing inhibitors, wetting agents, colorants or
pigments, thermoplastics, processing aids, UV blocking compounds,
fluorescent compounds, UV stabilizers, inert fillers, fibrous
reinforcements, antioxidants, impact modifiers including
thermoplastic particles, and mixtures thereof. The above list is
intended to be exemplary and not limiting. The preferred additives
for the, formulation of the present invention may be optimized by
one skilled in the art.
[0041] The curable composition can be prepared by any suitable
method known to those skilled in the art, such as, for example,
distillation or solvent extraction. The curable composition can
then be mixed with a hardener, another epoxy resin, and any other
component described above to form the curable composition in any
combination or subcombination.
End Use Applications
[0042] The curable composition can be used to prepare hot-melt
prepregs, where fibers are impregnated with solvent free, un-cured
or slightly cured epoxy formulations. A typical manufacturing
procedure involves (1) film manufacture and (2) film impregnation.
In film manufacture, the epoxy resin(s) are mixed at elevated
temperature (eg., from 50-150.degree. C.) with additive(s),
catalyst(s), hardener(s) and fabricated to the particular film
format. The formulations are mainly in the pre-polymer state with a
limited curing level (if any), and the films are protected by
paper/polyethylene release sheets. In film impregnation, the woven
or unidirectional fabrics are impregnated with the epoxy films
under heat to form prepregs. Prior to the curing, the prepregs are
somewhat similar to those sticky tapes covered with protective
sheets. Once the protective sheets are removed, multiple layers or
plies of the prepregs are stacked into a mold, or onto a mandrel to
form the desired shapes of the composite articles. Then the prepreg
materials undergo a thermal curing process under vacuum and/or
pressure to consolidate the laminates. A higher curing temperature
usually leads to rapid curing reaction kinetics, but may require
additional mold-cooling time, which enables the consolidated
laminates regain the sufficient stiffness for their removal from
the hot molds.
[0043] In various embodiments, the prepregs prepared from the
curable compositions have a glass transition temperature (T.sub.g)
that is equal to or greater than the final curing temperature when
the prepreg is cured for less than two hours. In various
embodiments, the curing conditions include a curing temperature in
the range of from 80.degree. C. to 200.degree. C. In various
embodiments, the T.sub.g is in the range of from 115.degree. C. to
215.degree. C.
[0044] Tack is the property of a semi-permanent adhesive that
allows it to adhere to another surface on immediate contact. With
regards to tack, the desired complex shear modulus (G*) ranges from
about 0.3 MPa to 0.03 MPa under 25.degree. C., 1 rad/s. When G* is
larger than 0.3 MPa, the uncured epoxy composition may lack of
adequate wetting capability to attach to the adherent. When G* is
smaller than 0.03 MPa, the uncured epoxy composition may lack of
adequate shear resistance to hold the prepreg on the vertical
adherent.
[0045] In an embodiment, prepregs are manufactured as follows:
sheets of carbon-fiber fabric pre-impregnated with somewhat sticky,
solvent-free, epoxy formulations are supplied in rolls. A
silicone-treated paper and/or polyethylene protective sheet is
sandwiched between the layers on the roll to prevent the pre-preg
from sticking to itself during storage and to facilitate handling
during the fabrication process.
[0046] The acceptable impregnation temperature ranges of the
hot-melt (solvent free) prepreg fabrication from about 60.degree.
C. to about 80.degree. C., which is at least 20.degree. C. lower
than the onset temperature of the exothermic curing reaction shown
in FIG. 1. Such impregnation temperature range is supposed to
reduce the undesired epoxy gelation prior to the composite
fabrication. The recommended processing viscosity level with the
aforementioned temperature range is from about 10 to about 3 Pa*s,
such that the fibers are still capable of being impregnated with
the epoxy composition with a good fiber wetting, even with the
presence of optional solid and viscous fillers, but without resin
dripping.
[0047] Examples of uses for the composite articles that can be
prepared with the hotmelt prepregs include, but are not limited to
sporting goods, aircrafts, and automobiles.
Examples
[0048] The following raw materials were used:
Experimental EPN--(E-EPN), high functional epoxy phenol novolac
with averages in the range of from 4.0 to 5.0 epoxide groups per
molecule (n=2.0 to 3.0 in Formula I above), with less than 5 weight
percent based on the of 2.0 epoxide groups per molecule
(2-functional). D.E.N..TM. 438--("DEN 438"), an EPN having an
average of 3.6 epoxide groups per molecule, available from the Dow
Chemical Company. D.E.N..TM. 431--("DEN 431"), an EPN having an
average of 2.8 epoxide groups per molecule, available from the Dow
Chemical Company. D.E.R..TM. 662--("DER 662"), a solid epoxy resin
available from the Dow Chemical Company. D.E.R..TM. 383--("DER
383"), a bisphenol A liquid epoxy resin available from the Dow
Chemical Company. Epon SU-8--("eBPAN"), epoxy bisphenol A novolac,
a multifunctional epoxy, available from the Momentive.
CG-1200--("DICY"), dicyandiamide, a latent curing agent available
from the Air Product and Chemical Inc. U415 M--("UREA"),
2,4-toluene bis dimethyl urea, a catalyst, available from the
Emerald Performance, CVC Thermoset Specialities.
[0049] In Examples 1 and 2, DEN 431 was heated to 70.degree. C. and
DICY and UREA were then added and mixed together by a
SpeedMixer.TM. (DAC150.1 FVZ-K, FlackTeK Inc.) at 2,300 rpm for 2
min, at least three runs or more, to obtain the homogeneous blend,
Blend-1. The E-EPN, DER 383 and DER 662 were heated to 120.degree.
C. and were mixed by the above SpeedMixer.TM. at 2,300 rpm for 2
min, at least three runs or more, to obtain the homogeneous blend,
Blend-2. Blend-1 was then poured into Blend-2, and the two blends
were mixed together using the above-mentioned SpeedMixer.TM. at 800
rpm for 30 sec, and then at 1,600 rpm for 1 min to obtain a
well-mixed formulation. The whole formulation was poured into a
pre-heated mold (about 120.degree. C.) to cast the 3 mm thick
plaques for further curing. The amounts of the components used in
Examples 1 and 2 are shown in Tables 1 and 2, respectively.
[0050] In comparative examples A and B, DEN 431 was heated to
70.degree. C. and DICY and UREA were then added and the components
were mixed using the above-mentioned SpeedMixer.TM. with 2,300 rpm,
2 min, at least three runs or more, to obtain the homogeneous
blend, Blend-1. DER 383 and DER 662 and epoxy bisphenol A novolac
(EBPAN) (EBPAN is used in Comparative Example B only) heated to
120.degree. C. and mixed together with the above SpeedMixer.TM.
with 2,300 rpm, 2 min, at least three runs or more, to obtain the
homogeneous blend, Blend-2. Blend-1 was then poured into the
Blend-2, and the two blends were then mixed by the above
SpeedMixer.TM. at 800 rpm for 30 sec, and then at 1,600 rpm for 1
min to obtain a well-mixed formulation. The whole formulation was
poured into the pre-heated mold (about 120.degree. C.) to cast the
3 mm thick plaques for further curing. The components were used in
the amounts shown in Table 1.
[0051] In comparative example C, DEN 431 was heated to 70.degree.
C. and DICY and UREA were then added and the components were mixed
using the above-mentioned SpeedMixer.TM. at 2,300 rpm for 2 min, at
least three runs or more, to obtain the homogeneous blend, Blend-1.
DEN 438 was heated to 120.degree. C. and was mixed with Blend-1
using the above SpeedMixer.TM. (DAC150.1 FVZ-K, FlackTeK Inc.) at
800 rpm for 30 sec, and then at 1,600 rpm for 1 min to obtain a
well-mixed formulation. The whole formulation was poured out into
the pre-heated mold (about 120.degree. C.) to cast the 3 mm thick
plaques for further curing.
[0052] For Comparative Examples A and B and Example 1, the curing
schedule used was 2 hours of 140.degree. C. isotherm curing in an
air circulation oven.
[0053] For Example 2 and Comparative Example C, the curing schedule
used was 2 hours of 160.degree. C. isotherm curing in an air
circulation oven.
TABLE-US-00001 TABLE 1 Comp-A Comp-B Ex-1 Part A (a1) Experimental
EPN 0 0 16 (g) (a2) DEN431(g) 19.8 19.8 19.8 (a3) DER383 (g) 32.1
25.7 25.7 (a4) DER662 (g) 48.1 38.5 38.5 (a5) eBPAN (g) 0 16 0
PartB (b1) DICY (g) 5.6 5.6 5.6 (b2) UREA (g) 2.8 2.8 2.8
T.sub.onset (.degree. C.) 118 117 118 T.sub.g (.degree. C.)
140.degree. C. cured 136 152 149 .eta.* @ 80.degree. C. (Pa * s)
9.2 11.4 7.4 G* @ 1 rad/s (MPa) 0.07 0.22 0.07 Flexure Modulus
(GPa) 3.14 3.08 3.27 K.sub.IC (MPa * m.sup.0.5) 1.02 0.85 0.85
TABLE-US-00002 TABLE 2 Comp-C Ex-2 Part A (a1) Experimental EPN 0
80.2 (a2) DEN431(g) 19.8 19.8 (a3) DER383 (g) 0 0 (a4) DER662 (g) 0
0 (a5) eBPAN 0 0 (a6) DEN438 (g) 80.2 0 PartB DICY (g) 5.6 5.6 UREA
(g) 2.8 2.8 T.sub.onset (.degree. C.) 117 117 T.sub.g (.degree. C.)
160.degree. C. cured 193 215 .eta.* @ 80.degree. C. (Pa * s) 1.5
6.4 G* @ 1 rad/s (MPa) 0.005 0.21 Flexure Modulus (GPa) 2.93 3.53
K.sub.IC (MPa * m.sup.0.5) 0.58 0.52
Characterizations
[0054] The functionality was determined by the GPC using a Viscotek
GP Max equipped with a TDA 302 detector array which included a
refractive index detector, a viscosity detector, and a RALLS (right
angle laser light scattering detector). Separation was achieved
using 2 PL gel 3 um mixed E, 300.times.7.5 mm analytical columns.
Tetrahydrofuran (THF), inhibited with 250 ppm BHT was used as the
mobile phase. The sample was dissolved in mobile phase (1%) and
filtered. The instrument was calibrated using Viscotek 115K
polystyrene standards.
[0055] A differential scanning calorimeter (TA Instruments Q2000)
was used for thermal analysis. The onset temperature of the
exothermic curing reaction, T.sub.onset, was obtained by conducting
a temperature sweep of 2.degree. C./min under nitrogen atmosphere
(flow rate=80 ml/min).
[0056] The dynamic mechanical thermal analysis (DMTA) was conducted
by using an advanced rheometric expansion system (ARES G2, TA
Instruments). The nominal dimension of the testing specimen was
12.7 mm.times.3.0 mm.times.40.0 mm. The testing temperature ranged
from 25 to 250.degree. C. and with a ramp rate of 3.degree. C./min.
The fixed testing frequency was 1 Hz and the strain amplitude was
0.1%. The peak of tan .delta. was reported as the Cured
T.sub.g.
[0057] A rotational rheometer (AR2000 ex. TA Instruments) was used
for the rheological study. The investigations were conducted by
using a stainless steel parallel plate (50 mm diameter, gap=800
.mu.m). The viscosity-temperature profile of the tested formulation
was monitored with the fixed ramp rate, oscillation frequency and
oscillation strain (2.degree. C./min, 1 Hz, and 0.5%,
respectively). A frequency sweep (0.1 to 100 Hz) at 25.degree. C.
was conducted to monitor the variation of the complex shear modulus
for the tack measurement.
[0058] The fracture toughness (K.sub.IC) and flexure modulus were
determined by following the testing guidance of ASTM D5045 and ASTM
D790, respectively.
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